Periodic Reporting for period 2 - EvoBias (Sex-specific demography and the evolution of gender-biased harmful cultural practices)
Berichtszeitraum: 2021-07-01 bis 2022-12-31
What is the problem being addressed?
Cultural practices that are harmful to one sex, but favour the other, are the focus of intense interest in the public eye, the social sciences and the evolutionary human sciences. Gender-biased behaviours, especially those that are harmful to women and girls, are often simply attributed to the low status of women. But this does not explain the diversity of gender-biased behaviours that we see around us. However the framework of behavioural ecology allows us to make formal predictions about how behaviour may vary in different circumstances. Some gender-biased practices do not fit the classic model of sexual conflict, in which males exploit females for their own mating advantage. We are also exploring an alternative explanation, which is sex-specific demography. This framework refocuses attention away from sexual selection, towards patterns of cooperation and conflict within families.
Why is this important for society?
Cultural practices that discriminate against some individuals or genders are ubiquitous globally. Our approach attempts to predict if different kinds of cultural traditions or cultural institutions are adaptations to particular ecological or social conditions. Conflicts of interest within the family appear to be a common theme in many of these practices. This has the potential to throw a somewhat novel light on how many of these behaviours arise, and persist.
What are the overall objectives?
EvoBias will develop and test new evolutionary demographic models that will focus on the role of sex-ratios, sex-biased dispersal and modes of marriage, in generating gender-biased harmful cultural practices. The behaviours to be studied include: female-biased workloads, witchcraft accusation, sending men to war, sending boys into monastic life, bride-capture and the ‘honour’ killing of women by their own kin. These represent both social issues and evolutionary puzzles. Through a combination of mathematical modelling, comparative studies using the literature and field-based sociodemographic studies, we seek evidence that sex-specific demography underpins these gender-biased harmful cultural traditions, somewhat refocussing how we might understand the resilience of such behaviours.
Cultural practices that are harmful to one sex, but favour the other, are the focus of intense interest in the public eye, the social sciences and the evolutionary human sciences. Gender-biased behaviours, especially those that are harmful to women and girls, are often simply attributed to the low status of women. But this does not explain the diversity of gender-biased behaviours that we see around us. However the framework of behavioural ecology allows us to make formal predictions about how behaviour may vary in different circumstances. Some gender-biased practices do not fit the classic model of sexual conflict, in which males exploit females for their own mating advantage. We are also exploring an alternative explanation, which is sex-specific demography. This framework refocuses attention away from sexual selection, towards patterns of cooperation and conflict within families.
Why is this important for society?
Cultural practices that discriminate against some individuals or genders are ubiquitous globally. Our approach attempts to predict if different kinds of cultural traditions or cultural institutions are adaptations to particular ecological or social conditions. Conflicts of interest within the family appear to be a common theme in many of these practices. This has the potential to throw a somewhat novel light on how many of these behaviours arise, and persist.
What are the overall objectives?
EvoBias will develop and test new evolutionary demographic models that will focus on the role of sex-ratios, sex-biased dispersal and modes of marriage, in generating gender-biased harmful cultural practices. The behaviours to be studied include: female-biased workloads, witchcraft accusation, sending men to war, sending boys into monastic life, bride-capture and the ‘honour’ killing of women by their own kin. These represent both social issues and evolutionary puzzles. Through a combination of mathematical modelling, comparative studies using the literature and field-based sociodemographic studies, we seek evidence that sex-specific demography underpins these gender-biased harmful cultural traditions, somewhat refocussing how we might understand the resilience of such behaviours.
Our work so far has focussed on four main areas.
a) Witchcraft accusation
Witchcraft beliefs are widespread and have the potential to cause great suffering. But it is a very hard topic to study, and the phenomenon itself can manifest in many forms. Postdoc Dr Sarah Peacey, with help from PhD student Olympia Campbell, have created a database of witchcraft accusation from 121 Bantu societies sub-Saharan Africa, which included 500 individual cases where a specific act of accusation of witchcraft was documented in the ethnographic literature where it was possible to identify the gender and other characteristics of the accuser and the accused. This dataset has enabled us to show that witchcraft accusations are gender specific and reflect competition for resources within families and communities (published in Scientific Reports).
b) Gender and honour-based violence.
Violence against women and girls, most of which is from their own partners or families, is a worldwide pandemic. PhD student Olympia Campbell has analysed demographic health survey (DHS) data testing whether there were different risk factors between intimate partner violence and natal family violence in a large sample of Jordanian women, including a focus on whether cousin marriage played any role. Cousin marriage and other forms of consanguinity is of particular interest as it has been associated with societies in which there are higher levels of 'honour-based' violence, including 'honour' killing, usually (but not exclusively) of young women, often by members of their own family (published in Evolution, Medicine and Public Health).
c) Gender biases in workload
Using data from an in-depth cross-cultural field study in rural China, we used accelerometers to gain accurate measures of the work burden of males and females in a set of different kinship systems, in some of which females disperse at marriage (the most common) and some of which males, or neither, or both sexes disperse at marriage. PhD student Yuan Chen is using this dataset to examine the influence of sex inequality generated by dispersal, kinship and sex ratio on gender balance in workload. We find that both being female and dispersing at marriage are predictive of high workloads. This supports the 'bargaining power hypothesis', which predicts that individuals lose bargaining power when they disperse away from their natal family and hence have to be more cooperative ie have to work harder. Globally most women experience the double workload penalty of both being female and being the dispersing sex (published in Current Biology).
d) Monastic celibacy for males
Monastic celibacy is an evolutionary puzzle. PhD student Erhao Ge, with our Chinese collaborators from Lanzhou University, have analysed our demographic data from Tibetan villages which shows that both the brothers of monks benefit and the fathers of monks have more children or grandchildren. Postdoc Alberto Micheletti has modelled in what cases celibacy could be shaped by inclusive fitness interests, and his modes show that celibacy is rarely favoured if the decision is made by the boy himself, but it can be favoured by his parents if there is a benefit to brothers. We show empirically these conditions are met; hence parent-offspring conflict appears to underpin the acceptance of sending young boys to these hugely influential religious institutions. The modelling and empirical findings which show how brothers benefit through gaining more parental resources when a brother goes to the monastery, published in Behavioral Ecology and Proc. Royal Society B. EG is now examining social networks between community members to see if there are any reputational benefits associated with being having a monk in the family. Overall, it appears that the practice is not costly to parents.
This work has also lead us to contribute to the wider debate on the role of inclusive fitness in how culture evolves. We have written two papers on how to think about and test the extent to which inclusive fitness interests do indeed shape human cultural behaviour (published in Behavioural Ecology (What is cultural evolution anyway?).
a) Witchcraft accusation
Witchcraft beliefs are widespread and have the potential to cause great suffering. But it is a very hard topic to study, and the phenomenon itself can manifest in many forms. Postdoc Dr Sarah Peacey, with help from PhD student Olympia Campbell, have created a database of witchcraft accusation from 121 Bantu societies sub-Saharan Africa, which included 500 individual cases where a specific act of accusation of witchcraft was documented in the ethnographic literature where it was possible to identify the gender and other characteristics of the accuser and the accused. This dataset has enabled us to show that witchcraft accusations are gender specific and reflect competition for resources within families and communities (published in Scientific Reports).
b) Gender and honour-based violence.
Violence against women and girls, most of which is from their own partners or families, is a worldwide pandemic. PhD student Olympia Campbell has analysed demographic health survey (DHS) data testing whether there were different risk factors between intimate partner violence and natal family violence in a large sample of Jordanian women, including a focus on whether cousin marriage played any role. Cousin marriage and other forms of consanguinity is of particular interest as it has been associated with societies in which there are higher levels of 'honour-based' violence, including 'honour' killing, usually (but not exclusively) of young women, often by members of their own family (published in Evolution, Medicine and Public Health).
c) Gender biases in workload
Using data from an in-depth cross-cultural field study in rural China, we used accelerometers to gain accurate measures of the work burden of males and females in a set of different kinship systems, in some of which females disperse at marriage (the most common) and some of which males, or neither, or both sexes disperse at marriage. PhD student Yuan Chen is using this dataset to examine the influence of sex inequality generated by dispersal, kinship and sex ratio on gender balance in workload. We find that both being female and dispersing at marriage are predictive of high workloads. This supports the 'bargaining power hypothesis', which predicts that individuals lose bargaining power when they disperse away from their natal family and hence have to be more cooperative ie have to work harder. Globally most women experience the double workload penalty of both being female and being the dispersing sex (published in Current Biology).
d) Monastic celibacy for males
Monastic celibacy is an evolutionary puzzle. PhD student Erhao Ge, with our Chinese collaborators from Lanzhou University, have analysed our demographic data from Tibetan villages which shows that both the brothers of monks benefit and the fathers of monks have more children or grandchildren. Postdoc Alberto Micheletti has modelled in what cases celibacy could be shaped by inclusive fitness interests, and his modes show that celibacy is rarely favoured if the decision is made by the boy himself, but it can be favoured by his parents if there is a benefit to brothers. We show empirically these conditions are met; hence parent-offspring conflict appears to underpin the acceptance of sending young boys to these hugely influential religious institutions. The modelling and empirical findings which show how brothers benefit through gaining more parental resources when a brother goes to the monastery, published in Behavioral Ecology and Proc. Royal Society B. EG is now examining social networks between community members to see if there are any reputational benefits associated with being having a monk in the family. Overall, it appears that the practice is not costly to parents.
This work has also lead us to contribute to the wider debate on the role of inclusive fitness in how culture evolves. We have written two papers on how to think about and test the extent to which inclusive fitness interests do indeed shape human cultural behaviour (published in Behavioural Ecology (What is cultural evolution anyway?).
To examine the origins of harmful cultural practices through the lens of evolutionary ecology is mostly beyond the state of the art. The prevailing view in the social sciences and in the general public is that harmful cultural practices are driven by cultural learning and cultural institutions (like religions), which cause individuals to behave in ways that do not necessarily promote their fitness or their well-being. However an alternative view is that families would not tolerate institutions that worked against their interests, and that there are in fact some benefits to at least some family members behind these cultural practices. Focussing on to what extent 'harmful' cultural practices might be shaped by inclusive fitness interests has lead us to broadly interpreting these practices in terms of conflicts of interest either between the sexes or within the family.
Over the second half of the project, we will continue to examine existing databases, including on honour killing and honour-based violence in Pakistan, and on sex ratios and workload in China. And we aim to create new databases from existing literature on global patterns of witchcraft accusations and on religious celibacy, to further elucidate their evolutionary and ecological determinants. We are working on a dataset collected on norms of honour-related violence from across 30 countries and how this associates with the frequency of cousin marriage.
We are also starting a new fieldwork phase of the project to examine bride-capture as a form of marriage in Kyrgyzstan. Bride-capture is a long-established form of marriage in Kyrgyzstan and some other mainly pastoralist societies. Postdoc Narhulan Halimbehke has joined the project in July 2022 to take this forward.
We plan to host several workshops to disseminate our results both in academia and beyond, in both the UK and in Kyrgyzstan. We aim to expose to a wider audience both through conferences and workshops, and academic publications, a book, articles for the media to a new perspective on gender-biased harmful practices, that opens up interpretations that are not generally used currently.
Over the second half of the project, we will continue to examine existing databases, including on honour killing and honour-based violence in Pakistan, and on sex ratios and workload in China. And we aim to create new databases from existing literature on global patterns of witchcraft accusations and on religious celibacy, to further elucidate their evolutionary and ecological determinants. We are working on a dataset collected on norms of honour-related violence from across 30 countries and how this associates with the frequency of cousin marriage.
We are also starting a new fieldwork phase of the project to examine bride-capture as a form of marriage in Kyrgyzstan. Bride-capture is a long-established form of marriage in Kyrgyzstan and some other mainly pastoralist societies. Postdoc Narhulan Halimbehke has joined the project in July 2022 to take this forward.
We plan to host several workshops to disseminate our results both in academia and beyond, in both the UK and in Kyrgyzstan. We aim to expose to a wider audience both through conferences and workshops, and academic publications, a book, articles for the media to a new perspective on gender-biased harmful practices, that opens up interpretations that are not generally used currently.